Quinnf,

I saw the same listing you referenced, and I kind of figured it was a misprint, but....

The last thing we need is someone importing "virtual" bombs

I have a "Machinerys Handbook" (22 ed.)Â here to reference from regarding flywheels:

P)228

Â Centrifugal Stresses in Flywheel Rims_

"The centrifugal tension or hoop tension stress which tends to rupture a flywheel rim of given area, depends solely upon the rim velocity, and is independent of the rim radius. The bursting velocity of a flywheel, based on hoop stress alone (not considering bending stresses), is related to the tensile stress in the flywheel rim by the following formula which is based on the centrifugal force formula from mechanics.

Â Â Â Â Â Â V = square root of (10xs) or, s = V squared divided by 10

where V = velocity of outside circumference of rim in feet per second, and s = the tensile strength of the rim material in pounds per square inch.

For cast iron having a tensile strength of 19,000 pounds per square inch the bursting speed would be:

V = square root of (10 x 19,000) = 436 feet per second"

The trouble with this formula is that it is based on (I think) a solid center (not spoked) wheel,

because on p230 & p231 there are charts that clearly state:

"Safe rim speed for "balance wheels"- heavy rims- 110 ft/sec and 6600 ft/min."

Also, on p230, it is stated:

"To find the safe speed in revolutions per minute, divide the safe rim speed in ft/min. by 3.14(pi) times the outside diameter of the flywheel rim in feet."

For the 16/1 @ 1000rpm w/ 27" flywheel engine in question:

6600ft/min divided by (3.14 x 2.25') = 933.7 rpm.....

..... for an engine rated at 1000 rpm....Buyer Beware

Also, as Quinnf pointed out, there in no way to know if the iron used in these is anywhere near the quality used in these formulas.

This is a damn good case why engineers use "safety factors" like 10x or MORE!!!

Get a copy of this book if you can!!!Â DON'T worry about the "edition" number!!! My Dad has one from~1950... This kind of mechanical and design information hasn't changed. New ones just have more "metric" info.

Curious what the deal is w/ these engines

Kevin